Medical retrieval devices generally are used to retrieve biological and foreign material, such as kidney stones and other calculi, from the body of a patient. Such medical retrieval devices may be used with an endoscope or a laparoscope. The use of such devices to capture foreign material like stones is made difficult by the freedom of movement of the stones within the body. A stone may dislodge from its resting place when contacted by a retrieval device. This may cause the stone to move into an area of the body that renders the stone inaccessible or undetectable, thus preventing the capture and removal of the stone.
Larger stones often need to be shattered because their size prohibits non-surgical removal from the body. Shattering a stone (by, for example, light, chemical, or physical energy) can disperse the resulting stone fragments from the original location of the stone. Stone fragments that are not removed from the body can form the nuclei for the formation of new stones. The dispersal of the fragments caused by the shattering process can cause fragments to move into inaccessible or unknown areas of the body, thus preventing or interfering with the capture and removal of the fragments.